If the heating element is rated at 1500 watts at 240v currnet draw would be 6.25 a.
Now if he ran this off his car battery which is 24 volts current draw would be 62.5 a.Would you agree?
No I would not agree. You are making the same error as the OP. A wattage rating is only valid for the voltage it was defined for. So 1500 watts at 240V can not be translated into 1500 watts at 24V.
So from the power rating the heater element has a resistance of 38.4 ohms.
Apply that with 24V and you get 0.625 Amps. That is a power of 15 watts.